My daughter and I were on holiday in the Uk in October and had entered the UK on australian passports. When she started to make her feelings known that she would like to stay there, I contacted immigration/border control who informed me that it did not matter at all that she had entered on an aussie passport....she was born in the UK and even though her British passport had expired (and this was still her child one) she was entitled to stay in the UK and live and work. She did not require a visa even though she had entered the country on an australian passport.
Yes you do need to have an NI number......We called the NI helpline....gave her name and as we had claimed child benefit in the UK till she was 10, she was on their system. All they had to do was reactivate her as being back in the UK and the NI number would be sent. It does take a while and after a month she still hasnt got it...main reason is the british gov can be incompetent like anywhere else and didnt send it when they said they were....so she is still waiting for it.. Yes couple of jobs wouldnt interview here without it...but others did. She has secured herself a permanent full time position as the place she is working know she is british. Her expired child passport and birth certificate are proof enough she is british and entitled to work and live in the UK. Since being there she has renewed her british passport which took less than 2 weeks to come through.
She lives in a shared house in the town where she works. No need for a car as she is lucky to have got a job 10 minutes walk from her front door. Public transport is good though in the area she is living.
She has moved back to our old home town, Newport Pagnell and has been reunited with so many of her old school friends from her primary days.
When she dropped the bombshell half through our holiday that she wanted to stay, well as many of you can imagine, it was pretty hard to get my head around. But at 19 she has to do things for herself now. I brought her to Australia at the age of 10, and she has had pretty much all her teen years here, and really wanted to experience whats left of them and some early adult life in the UK. But hey that was what we always wanted for our kids....the choice! Dual citizenship allowing them to be where they want...Australia or the UK.
Yes my flight home on my own was pretty emotional and of course I miss her badly, but I wouldnt have it any other way now....Its an experience of a lifetime for her....Having left a school a year ago and not really sure what she wants to do, hopefully how ever long she is over there will help her to make some decisions.
Yes its tough financially...be prepared to have to support them. Fortunately while she was on leave she didnt touch 4 weeks annual leave pay so that pretty much paid for her first months rent and deposit...but i have had to support her until she gets paid...which is this week!!! Woo!!!
Hope this has helped.